In the following, find the digits represented by the letters:
2 A
× A–––––––
1 2 A–––––––
In the given problem, the multiplication of A with A itself gives a number whose ones digit is A again. This happens only when A=1,5,6.
If A=1 then the multiplication will be 21×1=21. However, here the tens digit is given as 12, therefore, A=1 is not possible.
Similarly if
A=5 then the multiplication will be 25×5=125, therefore, A=5 is possible.
Hence, the letter A=5.